MÁLAGA, SPAIN — Scientists from Spain have discovered an Atlantic sawtail catshark embryo with two heads, a threatened shark species found only in the western Mediterranean. Their findings were recently published in the Journal of Fish Biology, leading the scientific community to wonder what may be causing these abnormalities.


In 2013, fishermen working off the Florida Keys caught a pregnant bull shark, and when they cut her open, they were stunned to find two unborn offspring, one of whom was a mutant. The fetus was the first two-headed bull shark on record. Most cases of the two-headed sharks are conceived by blue sharks, as they can have up to 50 babies at one time.


Scientists aren’t exactly sure what’s causing the bizarre birth defect, but theorize overfishing in some regions could be shrinking gene pools, leading to such physical abnormalities. Human pollution of the oceans may also play a role in these mutations.


Shark researchers say most of these misfit creatures don’t survive long after birth, and rarely even defy the odds to make it out of the womb.